Recursive module weirdness

module rec A_FF : sig
(*Call the following comment A_FF-1*)

(*           val a : int -> int *)

(*And the following comment A_FF-2 *)
(*           module B : functor (X : sig end) -> sig
               val c : int -> int
             end
 *)
         end
  = struct
(*Call the following comment A_FF-1*)
(*    let a x = x + (A_FF.a x)*)

(*And the following comment A_FF-2 *)
(*    module B (X : sig end)= struct
        let c _ = 0
      end
 *)
end


module rec A_TF : sig
(*Call the following comment A_TF-1*)

           val a : int -> int

(*And the following comment A_TF-2 *)
(*           module B : functor (X : sig end) -> sig
               val c : int -> int
             end
 *)
         end
  = struct
(*Call the following comment A_TF-1*)
    let a x = x + (A_TF.a x)

(*And the following comment A_TF-2 *)
(*    module B (X : sig end)= struct
        let c _ = 0
      end
 *)
end

module rec A_FT : sig
(*Call the following comment A_FT-1*)

(*           val a : int -> int *)

(*And the following comment A_FT-2 *)
           module B : functor (X : sig end) -> sig
               val c : int -> int
             end
         end
  = struct
(*Call the following comment A_FT-1*)
(*    let a x = x + (A_FT.a x)*)

(*And the following comment A_FT-2 *)
    module B (X : sig end)= struct
        let c _ = 0
      end

end


(** Comment out below this line, and everything compiles **)

module rec A_TT : sig
(*Call the following comment A_TT-1*)

           val a : int -> int

(*And the following comment A_TT-2 *)
           module B : functor (X : sig end) -> sig
               val c : int -> int
             end
         end
  = struct
(*Call the following comment A_TT-1*)
    let a x = x + (A_TT.a x)

(*And the following comment A_TT-2 *)
    module B (X : sig end) = struct
        let c _ = 0
      end
end